1. Field of the Invention
This invention relates to a device for holding two rotary elements, disposed alongside one another, stationary relative to one another.
The invention has been devised for the purpose of holding stationary relative to one another the camshafts of a double overhead camshaft internal combustion engine, such camshafts being driven in timed relation to the engine crankshaft by a toothed drive belt (timing belt) entrained around toothed pulleys or sprockets (herein called sprockets) on the shafts. With the aim of preventing failure in service and possible consequential engine damage, service schedules usually specify belt replacement at predetermined time and/or mileage intervals, and to ensure that the timing relationship between the cam shafts and the crankshaft of the engine is not lost the camshafts may have to be held against rotation relative to one another while the old belt is removed and a new one fitted. Other rotary elements driven by the timing belt may also have to be held against rotation during the replacement operation, for example if an engine is a compression-ignition engine and there is a fuel injection pump whose timed driving is effected by the belt.
Service tools for effecting such holding of the camshafts and/or other rotary elements of engines are available, but as supplied by motor manufacturers they are usually specifically designed for one engine or family of engines and are not usable for other engines. If a service establishment wishes to perform such work on many different engines but does not wish to keep a large number of special tools, there is a requirement for a more versatile holding device which is capable of being used on a wide range of engines. One problem in the design of such a more versatile holding device is that drive sprockets might be very close together, with very little space between them in which any part of a holding device can be disposed.